Unscheduled peer power save mode

ABSTRACT

Embodiments of unscheduled peer power save systems, devices and methods are disclosed. For example, a method of saving power for nodes configured to communicate via a direct link is provided. In one embodiment, among others, the method comprises forming, at an access point node (AP node), a indication frame for a client node, when no service period has occurred for the client node for a period of time at least equal to an indication window; sending the formed indication frame from the AP node to the client node through an access point; receiving, at the client node, the peer traffic indication from the access point; and determining, at the client node, that the AP node has traffic to send to the client node based on the indication frame.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 12/363,031,filed Jan. 30, 2009, which claims priority to U.S. ProvisionalApplication having Ser. No. 61/025,417, filed on Feb. 1, 2008, andcopending U.S. Provisional Application having Ser. No. 61/025,415, alsofiled on Feb. 1, 2008, all of which are incorporated herein by referencein its entirety.

TECHNICAL FIELD

The present disclosure is generally related to communication systems,and, more particularly, is related to wireless communication systems andmethods.

BACKGROUND

Wireless communication systems are widely deployed to provide varioustypes of wireless communication, such as voice, data, and so on, betweenvarious devices (also referred to as stations) such as cell phones,laptop computers, cameras, servers, desktop computers, etc. IEEE 802.11is a set of standards for wireless local area network (WLAN)communication between the devices, which is also sometimes referred toas wireless fidelity (WiFi). The devices fall into one of twocategories: access points and clients. An access point, normally arouter, is a base station for the wireless network that is connected toa wired network infrastructure. Clients are typically end devices, whichare referred to as stations.

Wireless communication has provided users with the ability tocommunicate with wireless devices without the constraints of a wiredconnection. To further facilitate mobility, many wireless devices, suchas cell phones, laptop computers, cameras, etc., also utilize mobilepower sources, such as batteries. As many of these wireless devicesutilize battery power, conserving power to extend battery life hasemerged as a priority.

SUMMARY

Embodiments of unscheduled peer power save systems, devices and methodsare disclosed. For example, a method of saving power for nodesconfigured to communicate via a direct link is provided. In oneembodiment, among others, the method comprises forming, at an accesspoint node (AP node), an indication frame for a client node, when noservice period has occurred for the client node for a period of time atleast equal to an indication window; sending the formed indication framefrom the AP node to the client node through an access point, receiving,at the client node, the indication frame from the access point; anddetermining, at the client node, that the AP node has traffic to send tothe client node based on the indication frame.

Other systems, methods, features, and advantages of the presentdisclosure will be or become apparent to one with skill in the art uponexamination of the following drawings and detailed description. It isintended that all such additional systems, methods, features, andadvantages be included within this description, and be within the scopeof the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the disclosed systems and methods can be betterunderstood with reference to the following drawings. The components inthe drawings are not necessarily to scale, emphasis instead being placedupon clearly illustrating the principles of the disclosed systems andmethods. Moreover, in the drawings, reference numerals designatecorresponding parts throughout the several views.

FIG. 1 is a block diagram of an exemplary communication environment inwhich embodiments of unscheduled peer power save mode (peer PSM) systemsand methods can be implemented.

FIG. 2 is a block diagram that illustrates an embodiment of anunscheduled peer PSM system embodied in one of the devices shown in FIG.1.

FIG. 3 is a schematic diagram of a general media access control (MAC)frame format defined in IEEE 802.11.

FIG. 4 is a schematic diagram of a frame control field of the generalMAC frame format defined in IEEE 802.11 and depicted in FIG. 3.

FIGS. 5-16 are flow charts that illustrate several embodiments ofmethods executed by the unscheduled peer PSM system shown in FIGS. 1 and2.

DETAILED DESCRIPTION

Disclosed herein are various embodiments of unscheduled peer power savemode (PSM) systems and methods wherein the battery life of a wirelessdevice can be improved for at least the reason that the wake time isreduced when compared to conventional techniques, among otheradvantages. In unscheduled peer PSM, a station and a peer station areconfigured to communicate over a direct link. A direct link is aconnection directly between two stations which are associated with thesame access point. The direct link enables peer to peer communicationbetween the two stations.

The stations may be in a low power state (e.g., a doze state) toconserve power when no data traffic is being transmitted between them.Depending on whether the stations have traffic to send to each other,the station and the peer station can start unscheduled service periodsduring which data traffic is sent between the stations over the directlink. Specifically, when a station has traffic to send to the peerstation, and no service period has occurred during an indication window,the station can notify the peer station by sending an indication frameto the peer station through the access point. The indication frameindicates the non-empty access categories (ACs) at the station. The peerstation receives the indication frame and determines that the peerstation should enter a more fully powered state (e.g., an awake state)and begin communicating with the station over the direct link. Hence, inunscheduled peer PSM, a station may be able to indicate to a peerstation the presence of buffered traffic instead of relying on theaccess point to perform this function. Further, in unscheduled peer PSM,both stations may be able to be in a power save mode at the same time.

Such unscheduled peer PSM systems and methods are described below in thecontext of IEEE 802.11 compliant communication systems, though theprinciples described herein can be extended to other communicationsystems and protocols and hence are not so limited. This description iswritten with reference to public documents IEEE Draft P802.11z_D0.1.doc,IEEE document IEEE802.11-2007.pdf (IEEE Std 802.11 ™-2007) and Wi-FiAlliance (WFA) document WMM_Specification_(—)1-1.doc (WMM™ (includingWMM™ Power Save) Specification version 1.1), which are all herebyincorporated by reference in their entirety.

FIG. 1 is a block diagram of an exemplary communication environment 100in which embodiments of unscheduled peer PSM can be implemented. Thecommunication environment 100 comprises a plurality of wireless andwired devices (or appliances), one or more of which may be configured tooperate as a wireless and wired device. One or more of the devices shownin FIG. 1 may incorporate unscheduled peer PSM systems and methods, asdescribed further below. Exemplary wireless devices include a cell phone102, a laptop computer 104 (which, along with other devices, maycommunicate with the cell phone 102 in a direct link mechanism asrepresented by direct link 114), and a digital camera 106. The wireddevices (e.g., with wireless capability) include a personal computer(PC) 108, a television 110, and a server 112. In the communicationenvironment 100 shown in FIG. 1, the cell phone 102 is in communication(e.g., radio frequency communication) with the laptop computer 104 andthe PC 108 via an access point 120, and the server 112 is communicationwith the television 110 via the access point 120. Also, the digitalcamera 106 is in communication with the laptop computer 104 and the PC108 via the access point 120. For instance, such communications may beused to load pictures from the digital camera 106 to the PC 108. Forillustrative purposes, the cell phone 102 is shown as an appliance thatembodies an embodiment of the unscheduled peer PSM device 200,illustrated in FIG. 2, as a client node, and the laptop computer 104 isshown as an appliance that embodies an embodiment of the unscheduledpeer PSM device 200 as an AP node. Wireless direct links 114 may beinstantiated between any of the devices shown in FIG. 1.

Note that communication between the various devices may employ one ormore of a plurality of protocols, including IEEE 802.11 (e.g., 802.11a,802.11b, 802.11e, 802.11g, 802.11n, 802.11z), WiMax, Ultra-Wide Band(UWB), Bluetooth, among other technologies. Additionally, although thecommunication environment 100 is shown as a basic service set (BSS)configuration, in some embodiments, communication among one or moredevices may be implemented using peer-to-peer networking, adhocnetworking, which is also referred to as independent basic service set(IBSS), and mesh networking (for instance as standardized in 802.11s),in lieu of or in addition to communication through the access point 120.In FIG. 1, the cell phone 102 and laptop computer 104 can communicatepeer-to-peer over the direct link 114.

FIG. 2 is a block diagram that illustrates an embodiment of anunscheduled peer PSM device 200 implemented in the cell phone 102 shownin FIG. 1, with the understanding that other devices may embody theunscheduled peer PSM device 200 in addition to, or in lieu of, the cellphone 102. Note that the devices shown in FIGS. 1 and 2 are exemplary innature, and that the unscheduled peer PSM device 200 may be implementedin any one of a plurality of different devices or appliances, includingcomputers (desktop, portable, laptop, etc.), consumer electronic devices(e.g., multi-media players, music players, portable sound recordingdevices, digital radio devices), cell phones, smart phones, compatibletelecommunication devices, personal digital assistants (PDAs), globalpositioning system (GPS) navigation systems, or any other type ofnetwork devices, such as printers, fax machines, scanners, hubs,switches, routers, set-top boxes, video game consoles, receivers,webcams, digital cameras, digital camcorders, televisions withcommunication capability, projectors, video servers, network attachedstorage (NAS) drives, roadside communication systems, robots, or any oneof a variety of other network devices. Unscheduled peer PSM may beapplied inside a house, a living room, an office, on a street, in ayard, a car, between a car and a roadside system, or in any one of avariety of other environments.

The unscheduled peer PSM device 200 can be implemented using digitalcircuitry, analog circuitry, or a combination of both, and is embodiedin one embodiment using a combination of hardware and software. As tohardware, one or more components of the unscheduled peer PSM device 200can be implemented with any or a combination of the followingtechnologies, which are all well known in the art: a discrete logiccircuit(s) having logic gates for implementing logic functions upon datasignals, an application specific integrated circuit (ASIC) havingappropriate combinational logic gates, a programmable gate array(s)(PGA), a field programmable gate array (FPGA), or one of a variety ofother technologies for implementing logic.

In one embodiment, the unscheduled peer PSM device 200 comprises amemory 202, a host processor (or media access controller in someembodiments) 204 executing code (e.g., a driver) referred to also as anupper MAC 206, and a network card 208 (e.g., network interface card orwireless card) coupled to the host processor 204, the network card 208comprising a processor or media access controller 209 executing codereferred to as a lower MAC 210, a baseband processor 211 coupled to theprocessor 209, a transceiver 212 coupled to the baseband processor 211,and an antenna 215 coupled to the transceiver 212. Note that theabove-described components of the unscheduled peer PSM device 200 arealso collectively referred to as a station or a node. In someembodiments, a station or a node may comprise fewer, additional ordifferent components.

Further, in some embodiments, the lower MAC 210 can be incorporated intothe baseband processor 211. The transceiver 212 comprises in oneembodiment such well-known transceiver components including filters,amplifiers (e.g., power amplifiers, switches, etc.). The host processor204 and processor (or media access controller) 209 may each be embodiedas a digital signal processor (DSP), a microprocessor, a general purposeprocessor, or an application specific integrated circuit (ASIC), amongothers devices. One having ordinary skill in the art should appreciatethat additional components not shown can be used (e.g., a host processorinterface, various busses, etc.), yet which are omitted for brevity.

In one embodiment, preparation, transmission, and reception of frames,as well as the determination of signal strength, is under the control ofthe lower MAC 210 as executed by the processor 209. In some embodiments,control of the aforementioned functionality is solely by either theupper MAC 206 or the lower MAC 210, and in some embodiments, theexecution of the MACs 206 and 210 may be implemented via a singleprocessor or on two or more processors. In some embodiments,functionality of the upper and lower MACs 206 and 210 may becollectively performed in a single MAC.

In one embodiment, the upper MAC 206 and lower MAC 210 each comprisesoftware (e.g., firmware) residing on the respective processors 204 and209, respectively, that is executed by a suitable instruction executionsystem. In some embodiments, functionality of the upper MAC 206 andlower MAC 210 may comprise software stored in memory (e.g., memory 202)or other computer readable medium (e.g., optical, magnetic,semiconductor, etc.), and executed by the host processor 204 or otherprocessor.

Wireless LANs are generally implemented according to the standarddefined by the ISO/IEC 8802-11 international standard (IEEE 802.11) forwireless systems operating in the 2.4-2.5 GHz ISM (industrial,scientific and medical) band, which is also referred to as IEEE Std802.11™-2007. FIG. 3 illustrates a general MAC frame format defined inIEEE 802.11. Each MAC frame includes a MAC header, a variable lengthframe body and a frame check sequence (FCS). As shown, the MAC headerincludes Frame Control, Duration/ID, Address 1, Address 2, Address 3,Sequence Control, Address 4 and quality of service (QoS) control fields.The FCS is appended after the frame body. The address fields in MACframe format are used to indicate the Basic Service Set identifier(BSSID), Source address (SA), Destination Address (DA), TransmitterAddress (TA), and Receiver Address (RA), depending on the direction ofthe frame (station to station, station to access point, access point tostation, or access point to access point, respectively). Thus, whenreceiving data frames transmitted in the wireless LANs, a stationoperating in a service set can detect the packets transmitted over awireless media (WM) and determine the intended recipient in accordancewith the destination information therein. A station waiting for dataframes needs to be powered in order to receive packets transmitted tothe station.

However, since most stations in the wireless network are mobile deviceswhich may be battery powered, power management becomes an importantconsideration in performance analysis. IEEE 802.11 provides a mechanismto support establishment and maintenance of the power management mode ofa station, wherein a station may be in one of two different powerstates: awake and doze. The station in the awake state is fully powered,while the station in the doze state is not able to transmit or receiveand consumes very low power. A station in power save mode may enter thedoze state, depending on the specific power save mode.

Also, Unscheduled Asynchronous Power Save Delivery (U-APSD) is amechanism for IEEE 802.11-based systems that was developed to helpwireless devices conserve power. According to U-APSD, the station sendsa trigger frame to the access point when the access point has indicatedthat it has buffered traffic for the station. The trigger frame is thenacknowledged by the access point. The station remains awake aftersending the trigger frame. At some time after receiving the triggerframe, the access point responds by sending buffered downlink traffic(e.g., data frames) to the station. On the final transmitted downlinkframe, the access point may set an End Of Service Period (EOSP) bit,which indicates to the station that the service period has ended andthat the station can return to a doze state, where at least one of theactive components utilized during normal operation is deactivated duringa period of communicative inactivity. Also, the access point may set theEOSP bit to terminate the service period when the access point has moredata buffered for the station. In U-APSD, the station may also send atrigger frame to the access point without first receiving an indicationfrom the access point that traffic is buffered.

Unscheduled peer PSM is a power save mode that can be used by a stationand a peer station that support Tunneled Direct Link Setup (TDLS) (IEEE802.11z). TDLS is characterized by the fact that the signaling framesare encapsulated in data frames, which allows them to be transmittedthrough an access point transparently. Therefore, a direct link can besetup using any access point. The access point does not need to bedirect link aware, nor does it have to support any of the capabilitiesthat will be used on the direct link. TLDS also includes an option toenter unscheduled peer PSM while remaining on the direct link, so thatthe station can enter a power save mode while the direct link remainslogically in place.

Stations capable of supporting unscheduled peer PSM may signal thiscapability in the Extended Capabilities Information Element in the framebody of a management frame like a beacon frame or an association requestframe. Section 7.3.2.27 of IEEE document IEEE802.11-2007.pdf describesthe Extended Capabilities Information Element in further detail. Table 1describes the manner in which a station signals whether the station iscapable of supporting unscheduled peer PSM.

TABLE 1 Extended Capabilities Information Fields Bit Information Notes<ANA> Peer PSM The Peer PSM AP mode capability bit set to 1 AP modeindicates that the station supports Peer PSM AP mode. The Peer PSM APmode capability bit set to 0 indicates that the station does not supportthis capability. <ANA> Peer PSM The Peer PSM client mode capability bitset to 1 client mode indicates that the station supports Peer PSM clientmode. The Peer PSM client mode capability bit set to 0 indicates thatthe station does not support this capability.

FIGS. 5-16 are flow charts illustrating various methods of saving powerfor stations configured to communicate via a direct link. One or more ofthe methods is executable by the devices illustrated in thecommunication environment 100 depicted in FIG. 1. For example, the cellphone 102, the laptop computer 104, and the access point 120 of FIG. 1may embody the client node, the AP node, and the access point,respectively, described below in the following embodiments. Further, insome embodiments, the unscheduled peer PSM device 200 described abovewith respect to FIG. 2 may be configured as the client node or the APnode. In other words, in some embodiments, the client node and the APnode store modules, segments, or portions of code including one or moreexecutable instructions for execution by a processor to implementspecific logical functions or blocks of the embodiments of the methodsdescribed below. Also, the AP node is not an access point but rather astation in an access point mode with respect to U-APSD. Further, theclient node is a station in client mode with respect to U-APSD.

FIG. 5 is a flow chart that illustrates a first embodiment of a methodof saving power for stations configured to communicate via a directlink. In FIG. 5, the method 500 includes blocks 510, 520, 530, 540, 550,and 560. In block 510, a data frame for the client node is received atan AP node. The AP node and the client node are associated with the sameaccess point. The AP node and the client node are stations that aredirect link peers, and the AP node is in an access point mode whereasthe client node is in a client mode with respect to U-APSD. Further, inblock 510, the client node may be in a doze state when the data frame isreceived by the AP node. Hence, the AP node cannot immediately transmitthe data frame to the client node over the direct link because theclient node may not be in an awake mode to receive the transmitted dataframe.

In block 520, an indication frame is formed at the AP node for theclient node, when no service period has occurred for the client node fora period of time at least equal to an indication window. The indicationframe may be referred to as a peer traffic indication frame. Anexemplary indication frame may include some or all of the informationshown below in Table 2.

TABLE 2 Exemplary Indication Frame Fields Order Fields Notes 1 LinkIdentifier The Link Identifier identifies the direct link 2 AC_VO 1octet field that indicates if AC_VO is backlogged backlogged (1) or not(0) 3 AC_VI 1 octet field that indicates if AC_VI is backloggedbacklogged (1) or not (0) 4 AC_BE 1 octet field that indicates if AC_BEis backlogged backlogged (1) or not (0) 5 AC_BK 1 octet field thatindicates if AC_BK is backlogged backlogged (1) or not (0)

The link identifier field of the exemplary indication frame in Table 2identifies a direct link through the AP node MAC address, the clientnode MAC address, and the basic service set identifier (BSSID), which isthe access point MAC address. The access category (AC) backlogged fieldsin Table 2 in the indication frame indicate whether a corresponding ACis backlogged for the client node. For example, as illustrated in Table2, AC backlogged fields for AC_VO, AC VI, AC_BE, and AC_BK may bepresent. AC_VO is the access category for voice type traffic; AC VI isthe access category for video type traffic; AC_BE is the access categoryfor best effort type traffic; and AC_BK is the access category forbackground type traffic.

In block 530, the formed indication frame is sent from the AP node tothe client node through an access point. The AP node stays in the awakestate after the formed indication frame is sent. In block 540, theindication frame is received at the client node, from the access point.In block 550, whether the AP node has traffic to send to the client nodeis determined at the client node. The determination is made based on thereceived indication frame. For example, the client node may determinewhether any of the AC Backlogged fields includes a non-zero value. Inblock 560, a service period is started by the client node by sending atrigger frame from the client node to the AP node over a direct linkresponsive to a determination by the client node that the AP node hastraffic to send to the client node. The trigger frame starts a serviceperiod.

FIG. 6 is a flow chart that illustrates a second embodiment of a methodof saving power for stations configured to communicate via a directlink. In FIG. 6, the method 600 includes blocks 610, 620, 630, 640, 650,660 and 670. In block 610, whether an AC is backlogged with traffic forthe client node is determined at an AP node.

In block 620, whether a service period has occurred for the AC for theclient node for a period of time at least equal to an indication windowis determined. In block 630, an indication frame is formed at the APnode responsive to a determination that an AC is backlogged with trafficfor the client node and a determination that no service period hasoccurred for the AC for the client node for a period of time at leastequal to the indication window. The formation of the indication frame inblock 630 is similar to the formation of the indication frame describedwith respect to block 520 above.

In block 640, the formed indication frame is transmitted from the APnode through the access point to the client node. The AP node stays inthe awake state after the indication frame is transmitted. In block 650,the indication frame is received at the client node from the accesspoint. In block 660, whether the AP node has traffic to send to theclient node is determined at the client node based on the indicationframe. In block 670, a service period is started by the client node bysending a trigger frame from the client node to the AP node over adirect link responsive to a determination that the AP node has trafficto send to the client node.

The duration of the indication window is defined such that it is not toolong to cause unwanted latency for buffered traffic and not too short togenerate too many indication frames. In some embodiments, the durationof the indication window is fixed. For example, the indication windowmay be 200 ms. In some embodiments, the duration of the indicationwindow is adjustable. For example, the duration of the indication windowmay be increased if the arrival time of frames at the client nodeexceeds the indication window. Also, the duration of the indicationwindow may be decreased if the arrival time of frames is less than theindication window. Further, the duration of the indication window may benegotiable by the client node and the AP node.

FIG. 7 is a flow chart that illustrates a third embodiment of a methodof saving power for stations configured to communicate via a directlink. In FIG. 7, the method 700 includes blocks 710, 720, 730, 740, 750,760 and 770. In block 710, a data frame for the client node is receivedat an AP node. The AP node and the client node are stations that areassociated with the same access point. The AP node and the client nodeare direct link peers of each other.

In block 720, an indication frame is formed at the AP node for theclient node, upon a determination by the AP node that no service periodhas occurred for the client node for a period of time at least equal toan indication window. The formation of the indication frame in block 720is similar to the formation of the indication frame described withrespect to block 520 above. In block 730, the formed indication frame issent from the AP node to the client node through the access point, andthe AP node stays in the awake state after the formed indication frameis sent. The AP node stays awake at least until a service period isstarted by the client node. In block 740, the indication frame isreceived at the client node from the access point. In block 750, whetherthe AP node has traffic to send to the client node is determined at theclient node based on the indication frame. In block 760, a first serviceperiod is started by sending a first trigger frame from the client nodeto the AP node over a direct link responsive to a determination that theAP node has traffic to send to the client node.

In block 770, a second service period is started by a second triggerframe being sent from the client node after the first service period hasended but before the expiry of a time period at least equal to anindication window. The time period may be measured from the start or theend of the first service period. For example, the final frame of thefirst service period may include an EOSP bit set to indicate that thefirst service period is ending and that the AP node will no longer besending data frames for the first service period to the client node. TheQoS Control field, depicted in the MAC header illustrated in FIG. 3,includes an EOSP field that can be used to indicate to a client nodethat no further data will be transmitted to that client node and that aservice period is terminated, for instance because no further data isbuffered for that client node. The QoS Control field is described inTable 3 below. For QoS Data and QoS Null frames, the EOSP field ispresent as bit 4 of the QoS Control field.

TABLE 3 QoS Control field Applicable Frame Bits (sub) Types 0-3 Bit 4Bits 5-6 Bit 7 Bits 8-15 QoS Data and QoS Null TID EOSP Ack ReservedReserved frames sent over the Policy direct link

The rules governing the sevice period may be the same as those definedin subclause 11.2.1.4 of IEEE Std 802.11™-2007 or in subclause 3.6 ofWMM™ (including WMM™ Power Save) Specification version 1.1.

After the frame including the EOSP bit set to indicate that the firstservice period is ending is received, a second service period is startedby a second trigger frame being sent from the client node to the AP nodeover the direct link. In some embodiments, the client node ensures thata new (e.g., second) service period is started before an indicationwindow expires, to avoid repeated transmission of indication frames. Inother words, the new service period is started before a secondindication frame is received.

The duration of the indication window is defined such that it is not toolong to cause unwanted latency for buffered traffic and not too short togenerate too many indication frames or service periods. In someembodiments, the duration of the indication window is fixed. Forexample, the indication window may be 200 ms. In some embodiments, theduration of the indication window is adjustable. For example, theduration of the indication window may be increased if the arrival timeof frames at the client node exceeds the indication window. Also, theduration of the indication window may be decreased if the arrival timeof frames is less than the indication window. Further, the duration ofthe indication window may be negotiable.

FIG. 8 is a flow chart that illustrates a fourth embodiment of a methodof saving power for stations configured to communicate via a directlink. In FIG. 8, the method 800 includes blocks 810, 820, 830, 840, 850,and 860. In block 810, a data frame for the client node is received atan AP node. The AP node and the client node are stations that areassociated with the same access point. The AP node and the client nodeare direct link peers.

In block 820, an indication frame is formed at the AP node for theclient node, when no service period has occurred for the client node fora period of time at least equal to the indication window. The formationof the indication frame in block 820 is similar to the formation of theindication frame described with respect to block 520 above. In block830, the indication frame is sent from the AP node to the client nodethrough an access point, and the AP node stays in the awake state afterthe formed indication frame is sent, at least until a trigger frame or aPS-Poll frame is received by the AP node from the client node. In block840, the indication frame is received at the client node from the accesspoint. In block 850, whether the AP node has traffic to send to theclient node based on the indication frame is determined at the clientnode. In block 860, a PS-Poll frame is sent to the AP node responsive toa determination, at the client node, that the AP node has traffic tosend to the client node. The PS-Poll frame is sent by the client node inorder to receive the buffered traffic from the AP node. Aftertransmitting the PS-Poll frame, the client node remains in the awakestate until a frame is received from the AP node, via the direct link.

FIG. 9 is a flow chart that illustrates a fifth embodiment of a methodof saving power for stations configured to communicate via a directlink. In FIG. 9, the method 900 includes blocks 910, 920, 930, 940, 950,960, and 970. In block 910, a data frame for the client node is receivedat an AP node. The AP node and the client node are stations that areassociated with the same access point. The AP node and the client nodeare peers of each other.

In block 920, an indication frame is formed at the AP node for theclient node. The formation of the indication frame in block 920 issimilar to the formation of the indication frame described with respectto block 520 above. In block 930, the formed indication frame is sentfrom the AP node to the client node through an access point. The AP nodestays in the awake state after the formed indication frame is sent. Inblock 940, the indication frame is received at the client node from theaccess point.

In block 950, whether the AP node has traffic to send to the client nodeis determined at the client node based on the indication frame. Forexample, the client node may determine whether any of the AC backloggedfields is set to a non-zero value. In block 960, a service period isstarted by a trigger frame being sent from the client node to the APnode over a direct link responsive to a determination that the AP nodehas traffic to send to the client node. In block 970, the AP node entersa sleep mode after the end of the service period.

FIG. 10 is a flow chart that illustrates a sixth embodiment of a methodof saving power for stations configured to communicate via a directlink. In FIG. 10, the method 1000 includes blocks 1010, 1020, 1030,1040, 1050, 1060, and 1070. In block 1010, a data frame for the clientnode is received at an AP node. The AP node and the client node arestations that are associated with the same access point. The AP node andthe client node are peers on a direct link. In block 1020, an indicationframe is formed at the AP node for the client node. The formation of theindication frame in block 1020 is similar to the formation of theindication frame described with respect to block 520 above. Theformation is triggered by the received data for the client node and theabsence of a service period for the AC and the client node of thereceived frame for a duration greater than an indication window.

In block 1030, the formed indication frame is sent from the AP node tothe client node through an access point. In block 1040, the indicationframe is received at the client node from the access point. In block1050, whether the AP node has traffic to send to the client node isdetermined at the client node based on the indication frame from the APnode. In block 1060, a service period is started by the client node bysending a trigger frame from the client node to the AP node over adirect link responsive to a determination that the AP node has trafficto send to the client node. In block 1070, the AP node stays awake atleast until a trigger frame is received from the client node.

FIG. 11 is a flow chart that illustrates a seventh embodiment of amethod of saving power for stations configured to communicate via adirect link. In FIG. 11, the method 1100 includes blocks 1110, 1120,1130, 1140, 1150, and 1160. In block 1110, a beacon sent by an accesspoint is checked by the client node, and the client node is in a powersave mode. In block 1120, whether the access point has a frame for theclient node is determined based on the checked beacon. A bit set in thebeacon indicates whether the access point has a frame for the clientnode.

In block 1130, a request is sent from the client node to the accesspoint requesting that the access point send the frame to the client noderesponsive to a determination that the access point has a frame for theclient node. In block 1140, the frame is received at the client nodefrom the access point. The frame is an indication frame. The indicationframe is discussed above with respect to Table 2. In block 1150, whetherthe AP node has traffic to send to the client node is determined at theclient node. In block 1160, a service period is started by sending atrigger frame from the client node to the AP node over a direct linkresponsive to a determination that the AP node has traffic to send tothe client node.

FIG. 12 is a flow chart that illustrates an eighth embodiment of amethod of saving power for stations configured to communicate via adirect link. In FIG. 12, the method 1200 includes blocks 1210, 1220,1230, 1240, 1250, and 1260. In block 1210, a beacon sent by an accesspoint is checked by the client node, and the client node is in a powersave mode.

In block 1220, whether the access point has a frame for the client nodeis determined based on the checked beacon. A bit set in the beaconindicates whether the access point has a frame for the client node. Inblock 1230, a request is sent from the client node to the access pointrequesting that the access point send the frame to the client noderesponsive to a determination that the access point has a frame for theclient node.

In block 1240, the frame is received at the client node from the accesspoint. The frame is an indication frame. In block 1250, whether the APnode has traffic to send to the client node is determined at the clientnode. In block 1260, a PS-Poll frame is sent from the client node to theAP node over a direct link responsive to a determination that the APnode has traffic to send to the client node.

FIG. 13 is a flow chart that illustrates a ninth embodiment of a methodof saving power for stations configured to communicate via a directlink. In FIG. 13, the method 1300 includes blocks 1310, 1320, 1330,1340, 1350, and 1360. In block 1310, whether an AC is backlogged withtraffic for a client node is determined at an AP node. In block 1320,whether a service period has occurred for the AC for the client node fora period of time at least equal to an indication window is determined atthe AP node.

In block 1330, an indication frame is formed at the AP node responsiveto a determination that the AC is backlogged and a determination that noservice period has occurred for the AC for the client node for a periodof time at least equal to the indication window. The formation of theindication frame in block 1330 is similar to the formation of theindication frame described with respect to block 520 above.

In block 1340, the formed indication frame is transmitted from the APnode through the access point to the client node. The AP node stays inthe awake state, after the indication frame is transmitted, at leastuntil a trigger frame is received from the client node. In block 1350, aservice period is started upon receiving a trigger frame from the clientnode. In block 1360, the AP node enters a doze state for a sleepinterval after the end of the service period. The transmission of framesbetween the client node and the AP node may be suspended during thesleep interval. In some embodiments, the duration of the sleep intervalis less than the indication window. In some embodiments, the duration ofthe sleep interval is longer than the indication window. Also, in someembodiments, the duration of the sleep interval is negotiable betweenthe client node and the AP node. Still, in some embodiments, theduration of the sleep interval is dependent upon a service interval fromthe traffic specification (TSPEC). In some embodiments, the duration ofthe sleep interval is also determined by the arrival of new traffic forthe client node.

In some embodiments, the duration of the indication window isadjustable. For example, the duration of the indication window may beincreased if the arrival time of frames at client node exceeds theindication window. Also, the duration of the indication window may bedecreased if the arrival time of frames is less than the indicationwindow.

FIG. 14 is a flow chart that illustrates a tenth embodiment of a methodof saving power for stations configured to communicate via a directlink. In FIG. 14, the method 1400 includes blocks 1410, 1420, 1430,1440, 1450, 1460, 1470, 1480, and 1490. In block 1410, a client nodelistens for a beacon sent by an access point during a listen interval.The client node is in a power save mode. In block 1420, an AP nodedetermines that an AC is backlogged with traffic for the client node andno service period has occurred during an indication window. In block1430, an indication frame is formed at the AP node for the client node.

In block 1440, the formed indication frame is sent from the AP node tothe access point. The AP node stays in an awake state after the formedindication frame is sent. In block 1450, the client node listens duringanother listen interval for a beacon sent by the access point. In block1460, whether the access point has a frame to send to the client nodebased on a bit set in the beacon sent by the access point is determinedat the client node. In block 1470, a request is sent from the clientnode to the access point requesting the frame be sent to the client noderesponsive to a determination that the access point has a frame to sendto the client node.

In bock 1480, the frame from the access point is received at the clientnode. The frame is an indication frame formed by the AP node. In block1490, a service period is started by sending a trigger frame from theclient node to the AP node over a direct link responsive to adetermination that the AP node has traffic to send to the client nodebased on the indication frame.

FIG. 15 is a flow chart that illustrates an eleventh embodiment of amethod of saving power for stations configured to communicate via adirect link. In FIG. 15, the method 1500 includes blocks 1510 and 1520.In block 1510, an AP node enters power save by sending a frame with thepower management (PM) bit set to a client node over a direct link. ThePM field, which includes the PM bit, is 1 bit in length and indicatesthe PM mode of the station. The PM field is included in the framecontrol field of the MAC header, as illustrated in FIG. 4. A value of 1indicates that the AP node will be in a power save mode. A value of 0indicates that the AP node will be in active (constantly awake) mode.The frame including the PM bit set in block 1510 includes the PM bit setto 1, to indicate that the AP node will be in a power save mode.

In block 1520, responsive to receiving the frame with the PM bit setfrom the AP node, the client node suspends direct transmissions to theAP node, until the occurrence of a service period. The service periodmay be triggered by the transmission of an indication frame by theclient node.

FIG. 16 is a flow chart that illustrates a twelfth embodiment of amethod of saving power for stations configured to communicate via adirect link. In FIG. 16, the method 1600 includes blocks 1610, 1620 and1630. In block 1610, a client node enters power save mode by sending afirst frame with the PM bit set to an AP node over a direct link. Thefirst frame including the power management bit set in block 1610includes the power management bit set to 1, to indicate that the clientnode will be in a power save mode.

In block 1620, the AP node enters a power save mode by sending a secondframe with the PM bit set to the client node. A value of 1 indicatesthat the AP node will be in a power save mode. A value of 0 indicatesthat the AP node will be in active (constantly awake) mode. The secondframe including the power management bit set in block 1620 includes thepower management bit set to 1, to indicate that the AP node will be in apower save mode. The second frame is transmitted during a service periodthat is initiated by the client node.

In block 1630, the AP node and the client node suspend directtransmissions until a service period occurs. The service period may betriggered by the transmission of an indication frame.

In the various embodiments discussed above with respect to FIGS. 5-16,traffic for an AC may be routed over the direct link while traffic foranother AC may be routed through the access point. If an AC carriestraffic that has high duty cycle relative to the traffic routed throughanother AC, it may be useful to route the traffic having the higher dutycycle over the direct link while the traffic having the lower duty cycleis routed through the access point. Video (VI) and voice (VO) trafficmay have a high duty cycle relative to background (BK) and best effort(BE), and traffic for AC VI and AC_VO is routed through the direct linkwhile traffic for AC_BK and AC_BE is routed through the access point.

Any process descriptions or blocks in flow diagrams shown in FIGS. 5-16should be understood as representing modules, segments, or portions ofcode which include one or more executable instructions for implementingspecific logical functions or steps in the process, and alternateimplementations are included within the scope of the embodimentsdescribed herein in which functions may be executed out of order fromthat shown or discussed, including substantially concurrently or inreverse order, depending on the functionality involved, as would beunderstood by those reasonably skilled in the art. Additionally, themethods illustrated in the flow charts of FIGS. 5-16 are not limited tothe system embodiments shown in FIGS. 1 and 2, but may be extended toother architectures and systems as should be appreciated by one havingordinary skill in the art in the context of this disclosure.

It should be emphasized that the above-described embodiments are merelypossible examples of implementations, merely set forth for a clearunderstanding of the principles of the disclosure. Many variations andmodifications may be made to the above-described embodiment(s) withoutdeparting substantially from the scope of the disclosure. All suchmodifications and variations are intended to be included herein withinthe scope of this disclosure.

At least the following is claimed:
 1. A method, comprising: receiving,at a second station, a first frame from a first station, the first framehaving a power management (PM) bit equal to 1; and responsive toreceiving the first frame, suspending, at the second station, directtransmissions to the first station until the occurrence of a firstservice period, wherein the first service period is triggered by a firstindication frame transmitted by the second station to the first stationvia an access point (AP) when no data has been exchanged between thefirst station and the second station for a period of time at least equalto an indication window, and wherein the first and second stations areconfigured to communicate via a direct link or via the access point. 2.The method of claim 1, wherein the first indication frame is a unicastframe.
 3. The method of claim 1, wherein the first frame is sent overthe direct link.
 4. The method of claim 1, wherein the second stationenters a power save mode by sending a second frame with the PM bit equalto 1 to the first station, via the direct link.
 5. The method of claim4, wherein the second frame is transmitted during a second serviceperiod.
 6. The method of claim 5, wherein the second service period istriggered by the transmission of a second indication frame to the firststation, by the second station, via the AP.
 7. The method of claim 4,wherein the second station stays awake after transmitting a thirdindication frame.
 8. The method of claim 1, wherein the first indicationframe is transmitted by the second station when the second station has aframe to send to the first station.
 9. A device comprising: a processor,the processor configured to: receive a first frame from a first station,the first frame having a PM bit equal to 1; and suspend directtransmissions to the first station until the occurrence of a firstservice period, wherein the first service period is triggered by a firstindication frame transmitted by the device to the first station via anaccess point (AP) when no data has been exchanged between the firststation and the device for a period of time at least equal to anindication window, and wherein the first station and the device areconfigured to communicate via a direct link or via the access point. 10.The device of claim 9, wherein the first indication frame is a unicastframe.
 11. The device of claim 9, wherein the processor is furtherconfigured to receive the first frame via the direct link.
 12. Thedevice of claim 9, wherein the device enters a power save mode bysending a second frame with the PM bit equal to 1 to the first station,via the direct link.
 13. The device of claim 12, wherein the secondframe is transmitted during a second service period.
 14. The device ofclaim 13, wherein the second service period is triggered by thetransmission of a second indication frame to the first station, by thedevice, via the AP.
 15. The device of claim 12, wherein the device staysawake after transmitting a third indication frame.
 16. The device ofclaim 9, wherein the first indication frame is transmitted by the devicewhen the device has a frame to send to the first station.
 17. Anapparatus comprising: a processor, the processor configured to: enter apower save mode by sending a first frame to a second station over adirect link, the first frame having a PM bit equal to 1, wherein theapparatus and the second station are configured to communicate via thedirect link or via the access point; and send a trigger frame to thesecond station via the direct link responsive to receiving a firstunicast indication frame from the second station via an access point,the trigger frame starting a first service period between the apparatusand the second station.
 18. The apparatus of claim 17, wherein theprocessor is further configured to suspend transmissions to the secondstation responsive to receiving a second frame with a PM bit equal to 1from the second station, via the direct link.
 19. The apparatus of claim17, wherein the processor is further configured to suspend transmissionsto the second station until the occurrence of a second service period.20. The apparatus of claim 17, wherein the second frame is receivedduring a third service period.